Definition
A graph showing how a magnetic material responds to a magnetizing force. The horizontal axis (H) represents the strength of the magnetizing force applied to the material, and the vertical axis (B) represents the resulting magnetic flux density inside the material. The curve reveals how easily the material becomes magnetized, the point at which it saturates, and how much magnetism it retains when the magnetizing force is removed.
Plain English
A chart that shows how strongly a piece of metal becomes magnetized when you apply a magnetic force to it, and how much of that magnetism stays behind after you take the force away.
Context Anchor
Seen in aircraft electrical and ignition-system theory, especially when discussing magnetos, generators, transformers, and iron cores.
Derivation
The letters come from physics notation: H is the symbol for magnetizing force (also called magnetic field intensity), and B is the symbol for the resulting magnetic flux density. The curve simply plots B against H, hence 'B-H curve.'
Why Pilots Care
Understanding residual magnetism in aircraft structures helps explain and correct compass errors during compensation.
Analogy
Think of stretching a rubber band. A small pull produces a small stretch, more pull produces more stretch, and eventually the band reaches a limit where extra pulling adds almost nothing. A B-H curve shows the same kind of relationship between magnetic 'pull' and magnetic 'stretch' inside a material.
Grounding Statement
Picture increasing current through a coil around an iron core and watching how strongly the core becomes magnetized.
Intuition Check
Do not read “curve” here as a turn or flight path. A B-H curve is a magnetism graph, not an aircraft maneuver or performance curve.
Example Sentence 1
The technician selected a core material with a steep B-H curve to ensure the magneto produced a strong spark at low engine speeds.
Example Sentence 2
During the compass swing procedure the technician used the material's B-H curve to estimate deviation caused by the airframe.